The studs are the way to go. If you run bolts, you're going to be taking a steel bolt out of an aluminum cylinder every time you pull the head. This will eventually strip every threaded hole in the cylinder. Four strokes use bolts for many reasons. Some cylinders use the bolt hole as an oil passage. That's why the bolt is necked down. Another reason is that most four stroke engines have limited clearance between the frame and head. If the cases had studs, you would never be able to remove the head and cylinder without pulling the engine. Not all four strokes use bolts. Some of them use long studs. Your best bet is to repair the stripped hole in the cylinder and install studs with a little bit of red thread locker.
